Numerical analysis of a three-wave-mixing Josephson traveling-wave parametric amplifier with engineered dispersion loadings

The recently proposed Josephson traveling-wave parametric amplifier (JTWPA) based on a ladder transmission line consisting of radio-frequency superconducting quantum interference devices and exploiting three-wave mixing has great potential in achieving both a gain of 20 dB and a flat bandwidth of at least 4 GHz. To realize this concept in practical amplifiers, we model the advanced JTWPA circuit with periodic modulation of the circuit parameters (engineered dispersion loadings), which allow the basic mixing process, i.e., omega(s) = omega(p) - omega(i), where omega(s), omega(p), and omega(i) are the signal, the pump, and the idler frequencies, respectively, and efficiently suppress propagation of unwanted higher tones, including omega(2p) = 2 omega(p), omega(p+s) = omega(p) + omega(s), omega(p+i) = omega(p) + omega(i), etc. The engineered dispersion loadings allow achieving a sufficiently wide 3 dB-bandwidth from 3 to 9 GHz combined with a reasonably small ripple (+/- 2 dB) in the gain-vs-frequency dependence.